A Cracked fishing urn can be created at 2 Crafting and must be activated with a water rune. When fishing with a cracked fishing urn (r) in your inventory it is used with the Fishing skill to help with gaining experience.
The urn is filled when the player has earned 750 Fishing xp with the urn in inventory.
Once the cracked fishing urn is full, it becomes a cracked fishing urn (full) and can be teleported to Ernie for 150 Fishing experience.